Human genome integrity depends on many processes to ensure the fidelity of the duplication of DNA. The efficiency of these processes is crucial since errors in DNA can often be key to disease onset. An important process to insure genome integrity is the repair of damaged DNA. There are several types of DNA damage including (but not limited to): alkylation, oxidation, hydrolysis, adduct formation, base mismatch, among others. Alkylated DNA bases may be removed by two main routes: excision of the damaged base and activation of the base excision repair (BER) process, or direct dealkylation. The former route involves several enzymes involved in the BER cascade. The latter route may be performed by the AlkB family of enzymes. AlkB family enzymes are non-heme iron and ?-ketoglutarate dependent enzymes that perform an oxidative dealkylation of DNA. Some cancer treatments involve alkylating agents, and attempts have been made to enhance these therapies by inhibiting alkylating damage repair. Information gained from a detailed understanding of the structure and reaction mechanism of AlkB family proteins can aid in the development of inhibitors for these enzymes by providing useful information to develop transition state analogue inhibitors. One approach for this is via computational methods, including quantum mechanical/molecular mechanical (QM/MM) methods. Currently, most QM/MM implementations employ force fields that may not accurately describe the MM environment at close range, are not polarizable and lack methods to include long-range electrostatic effects. Our long-term goal is to understand the mechanism, structure and function of enzymes involved in DNA repair by means of computational simulations. To this end, the goals of the present proposal are: i) To study the structure/function/reactivity of AlkB family of enzymes by quantum mechanical/molecular mechanical (QM/MM), molecular dynamics (MD) and homology modeling. ii) To develop the first QM/MM program that interfaces a QM program with a two advanced force fields (GEM and AMOEBA) to accurately describe the MM environment; and to develop a novel method to introduce long-range electrostatic effects in QM/MM simulations. The detailed understanding of the structure, function and reaction mechanism of AlkB and its human homologues will provide insights into possible methods to inhibit these enzymes. Our collaborators, Prof. Robert Housinger and Prof. Thomas Hollis, will perform experimental studies based on our computational results. Profs. Pengyu Ren and David Case will provide assistance with the QM/MM implementation in the AMBER suite of programs. The successful completion of the proposed project will provide an accurate computational tool for the calculation of enzyme reactions, and the generation of structural and mechanistic insights on an important family of enzymes that may be used to enhance the efficacy of cancer treatments.

Public Health Relevance

The maintenance of genome integrity is crucial since errors in the genome can often be key for development of diseases. Therefore, the detailed understanding of DNA repair mechanisms for different DNA damage (e.g., radiation, alkylation, etc.) is extremely important. This project investigates the structure, function and mechanism by which the AlkB family of enzymes repair DNA that has been damaged by alkylating agents and focuses on the development of novel computational methods for the simulation of reaction mechanisms in enzymes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM108583-05
Application #
9250201
Study Section
Special Emphasis Panel (ZRG1-MSFD-N (08)F)
Program Officer
Wehrle, Janna P
Project Start
2014-05-01
Project End
2019-03-31
Budget Start
2017-04-01
Budget End
2018-03-31
Support Year
5
Fiscal Year
2017
Total Cost
$225,311
Indirect Cost
$71,411
Name
University of North Texas
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
614168995
City
Denton
State
TX
Country
United States
Zip Code
76203
Silvestrov, Pavel; Cisneros, G Andrés (2018) Insights into conformational changes in AlkD bound to DNA with a yatakemycin adduct from computational simulations. Theor Chem Acc 137:
Gahlon, Hailey L; Walker, Alice R; Cisneros, G Andrés et al. (2018) Reduced structural flexibility for an exonuclease deficient DNA polymerase III mutant. Phys Chem Chem Phys 20:26892-26902
Silvestrov, Pavel; Maier, Sarah J; Fang, Michelle et al. (2018) DNArCdb: A database of cancer biomarkers in DNA repair genes that includes variants related to multiple cancer phenotypes. DNA Repair (Amst) 70:10-17
Gökcan, Hatice; Kratz, Eric; Darden, Thomas A et al. (2018) QM/MM Simulations with the Gaussian Electrostatic Model: A Density-based Polarizable Potential. J Phys Chem Lett 9:3062-3067
Antczak, Nicole M; Walker, Alice R; Stern, Hannah R et al. (2018) Characterization of Nine Cancer-Associated Variants in Human DNA Polymerase ?. Chem Res Toxicol 31:697-711
Torabifard, Hedieh; Cisneros, G Andrés (2017) Computational investigation of O2 diffusion through an intra-molecular tunnel in AlkB; influence of polarization on O2 transport. Chem Sci 8:6230-6238
Walker, Alice R; Cisneros, G Andrés (2017) Computational Simulations of DNA Polymerases: Detailed Insights on Structure/Function/Mechanism from Native Proteins to Cancer Variants. Chem Res Toxicol 30:1922-1935
Liu, Monica Yun; Torabifard, Hedieh; Crawford, Daniel J et al. (2017) Mutations along a TET2 active site scaffold stall oxidation at 5-hydroxymethylcytosine. Nat Chem Biol 13:181-187
Walker, Alice R; Silvestrov, Pavel; Müller, Tina A et al. (2017) ALKBH7 Variant Related to Prostate Cancer Exhibits Altered Substrate Binding. PLoS Comput Biol 13:e1005345
Kratz, Eric G; Walker, Alice R; Lagardère, Louis et al. (2016) LICHEM: A QM/MM program for simulations with multipolar and polarizable force fields. J Comput Chem 37:1019-29

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